The following table lists the Active Directory Schema and its corresponding Object Version. If you are running Windows 2008 R2, the Object Version should be 47.

If you extended the schema using a beta version of Windows 2008 or Vista CD, you will see the ObjectVersion as 39. The ADPREP folder and ldf files were included in the Vista CD. You can see one of my old blogs about this - http://portal.sivarajan.com/2006/10/adprep-folder-and-files-on-vista-cda.html. Schema Version 39 is not supported so it is recommended to upgrade the Schema to Windows 2008 (44) or Windows 2008 R2 (47).

Windows 8 Update – 9/15/2011 9:24:15 PM

I guess it is the time to update blog with Windows 8 Objectversion information. The ObjectVersion in Windows 8 is 51.